Establish fork-owned CI before re-enabling GitHub Actions

[berghtho]

GitHub Actions is disabled at repository level because inherited workflows include upstream-oriented release, relay, mobile, AUR, preview, and deployment automation.

Before re-enabling Actions:

• choose fork-owned runners and trusted action policy
• identify a minimal side-effect-free CI workflow
• review every inherited workflow and keep publication/deployment workflows disabled
• protect production environments with manual approval
• run one fork-local PR to establish actual check names
• add only stable fork-owned checks to main branch protection
• document the approved workflow set in docs/internals/downstream-fork.md

No workflow should be enabled merely to inherit source behavior.